9.8 Acknowledgments

I am indebted to John Malcolm, Roddy Regan, Clare Ellis, Heather James and David Caldwell for their comments on an early draft of this paper. The paper was then amended and updated after discussion with David Caldwell, Heather James, Colin Breen and Piers Dixon, and comments from Roddy Regan, Richard Oram and Andrew Bicket. Any errors, of course, remain my own.